1. Technical Field
The present invention relates to a liquid ejecting head, a liquid ejecting apparatus including the head, and a piezoelectric element. More specifically, the present invention relates to a piezoelectric element which may be used in a liquid ejecting head and apparatus with improved displacement and discharging properties.
2. Related Art
One example of a liquid ejecting head currently known in the art is a ink jet recording head. In such ink jet recording heads, a diaphragm constitutes a part of a pressure-generating chamber that communicates with a nozzle orifice for discharging ink drops, and a piezoelectric element deforms the diaphragm to pressurize ink in the pressure-generating chamber in order to discharge ink droplets through the nozzle orifice. In some of piezoelectric elements used in the ink jet recording heads, a piezoelectric layer made of a piezoelectric material exhibiting an electromechanical transducing function, such as piezoelectric ceramics, is disposed between two electrodes. Such a piezoelectric element is mounted on a liquid ejecting head as a flexure-vibration-mode actuator.
In some liquid ejecting heads, lead zirconate titanate (PZT) having high displacement characteristics is used as piezoelectric ceramics (see JP-A-2001-223404). One problem with these configurations, however, is that the lead results in environmental pollution. As such, there has been an increased demand for piezoelectric ceramics and liquid ejecting heads with a reduced amount of lead and other harmful substances. For example, as piezoelectric ceramics not containing lead, BaTiO3 having a perovskite structure represented by ABO3 is known (for example, see JP-A-2000-72539).
However, the piezoelectric property of BaTiO3 is not sufficient for use as the piezoelectric element of a liquid ejecting head, and therefore a further improvement has been needed. Accordingly, for example, it is proposed to improve withstand-voltage characteristics by adding calcium titanate (CaTiO3) to barium titanate (BaTiO3), such as described in JP-A-6-279110.
However, even when piezoelectric ceramics of BaTiO3 to which CaTiO3 is added are used in piezoelectric elements, since the displacement characteristics are insufficient, there is a problem that ink jet recording heads cannot be provided with sufficient ejection characteristics.